There are some gold and white balls in a box. If 10 gold balls are removed from the box, the total number of balls left will be 8 times the number of gold balls left. If 40 white balls are removed from the box, the total number of balls left will be 3 times the number of gold balls. How many balls are there in the box?
|
Case 1 |
Case 2 |
|
Gold balls |
White balls |
Gold balls |
White balls |
Before |
1 u + 10 |
7 u |
1 p |
2 p + 40 |
Change |
- 10 |
|
|
- 40 |
After |
1 u |
7 u |
1 p |
2 p |
Number of white balls in the end for Case 1
= 8 u - 1 u
= 7 u
Number of gold balls in the end for Case 2
= 3 p - 1 p
= 2 p
The number of gold balls at first is the same for Case 1 and Case 2.
The number of white balls at first is also the same for Case 1 and Case 2.
1 u + 10 = 1 p --- (1)
7 u = 2 p + 40
7 u - 40 =
2 p --- (2)
Make p the same.
(1)
x2 2 u + 20 =
2 p --- (3)
(2) = (3)
7 u - 40 = 2 u + 20
7 u - 2 u = 20 + 40
5 u = 60
1 u = 60 ÷ 5 = 12
Number of balls in the box
= (1 u + 10) + 7 u
= 8 u + 10
= (8 x 12) + 10
= 96 + 10
= 106
Answer(s): 106